Soil-free systems for growing plants include hydroponic systems and aeroponic systems. In hydroponic systems, the roots of cultivated plants are suspended in a nutrient solution, while in aeroponic systems plant roots are generally suspended in the air and provided with a nutrient solution by spraying. Both types of systems avoid the use of soil or an aggregate medium.
The basic principle of aeroponic growing is to grow plants suspended in a closed or semi-closed environment by spraying the plant's roots and lower stem with an atomized or sprayed, nutrient-rich aqueous solution. The leaves and crown of growing plants extend above the roots, and for larger plants, trellising is used to suspend the weight of vegetation and fruit.
Both hydroponic and aeroponic systems, however, have disadvantages, including cost, scalability, and limitations on the variety of plants that can be cultivated. In view of the shrinkage of arable land in the world and significant population growth, improved soil-free cultivation methods are needed.